diff --git a/Cargo.lock b/Cargo.lock
index 39fba4fa731..b3afaaa35c0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4783,6 +4783,7 @@ dependencies = [
"rustc_middle",
"rustc_parse_format",
"rustc_query_system",
+ "rustc_serialize",
"rustc_session",
"rustc_span",
"rustc_target",
diff --git a/compiler/rustc_middle/src/infer/canonical.rs b/compiler/rustc_middle/src/infer/canonical.rs
index 7f3567c08be..43583b5723e 100644
--- a/compiler/rustc_middle/src/infer/canonical.rs
+++ b/compiler/rustc_middle/src/infer/canonical.rs
@@ -339,6 +339,12 @@ TrivialTypeTraversalAndLiftImpls! {
}
impl<'tcx> CanonicalVarValues<'tcx> {
+ /// Creates dummy var values which should not be used in a
+ /// canonical response.
+ pub fn dummy() -> CanonicalVarValues<'tcx> {
+ CanonicalVarValues { var_values: Default::default() }
+ }
+
#[inline]
pub fn len(&self) -> usize {
self.var_values.len()
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 032cbb01ffb..00225a60d83 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -1113,17 +1113,6 @@ impl<'tcx, T> Binder<'tcx, T> {
if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
}
- pub fn no_bound_vars_ignoring_escaping(self, tcx: TyCtxt<'tcx>) -> Option<T>
- where
- T: TypeFoldable<'tcx>,
- {
- if !self.0.has_escaping_bound_vars() {
- Some(self.skip_binder())
- } else {
- self.0.try_fold_with(&mut SkipBindersAt { index: ty::INNERMOST, tcx }).ok()
- }
- }
-
/// Splits the contents into two things that share the same binder
/// level as the original, returning two distinct binders.
///
diff --git a/compiler/rustc_trait_selection/Cargo.toml b/compiler/rustc_trait_selection/Cargo.toml
index 67613e1a4eb..90d879976c2 100644
--- a/compiler/rustc_trait_selection/Cargo.toml
+++ b/compiler/rustc_trait_selection/Cargo.toml
@@ -19,6 +19,7 @@ rustc_infer = { path = "../rustc_infer" }
rustc_lint_defs = { path = "../rustc_lint_defs" }
rustc_macros = { path = "../rustc_macros" }
rustc_query_system = { path = "../rustc_query_system" }
+rustc_serialize = { path = "../rustc_serialize" }
rustc_session = { path = "../rustc_session" }
rustc_span = { path = "../rustc_span" }
rustc_target = { path = "../rustc_target" }
diff --git a/compiler/rustc_trait_selection/src/lib.rs b/compiler/rustc_trait_selection/src/lib.rs
index 081ac966c69..6fa09410363 100644
--- a/compiler/rustc_trait_selection/src/lib.rs
+++ b/compiler/rustc_trait_selection/src/lib.rs
@@ -21,6 +21,7 @@
#![feature(never_type)]
#![feature(result_option_inspect)]
#![feature(type_alias_impl_trait)]
+#![feature(min_specialization)]
#![recursion_limit = "512"] // For rustdoc
#[macro_use]
diff --git a/compiler/rustc_trait_selection/src/solve/assembly.rs b/compiler/rustc_trait_selection/src/solve/assembly.rs
index ba68da0686f..cd6e4d2bccd 100644
--- a/compiler/rustc_trait_selection/src/solve/assembly.rs
+++ b/compiler/rustc_trait_selection/src/solve/assembly.rs
@@ -1,38 +1,84 @@
//! Code shared by trait and projection goals for candidate assembly.
use super::infcx_ext::InferCtxtExt;
-use super::{
- instantiate_canonical_query_response, CanonicalGoal, CanonicalResponse, Certainty, EvalCtxt,
- Goal,
-};
+use super::{CanonicalResponse, Certainty, EvalCtxt, Goal};
use rustc_hir::def_id::DefId;
-use rustc_infer::infer::TyCtxtInferExt;
-use rustc_infer::infer::{
- canonical::{CanonicalVarValues, OriginalQueryValues},
- InferCtxt,
-};
use rustc_infer::traits::query::NoSolution;
use rustc_middle::ty::TypeFoldable;
use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_span::DUMMY_SP;
use std::fmt::Debug;
/// A candidate is a possible way to prove a goal.
///
/// It consists of both the `source`, which describes how that goal would be proven,
/// and the `result` when using the given `source`.
-///
-/// For the list of possible candidates, please look at the documentation of
-/// [super::trait_goals::CandidateSource] and [super::project_goals::CandidateSource].
#[derive(Debug, Clone)]
-pub(super) struct Candidate<'tcx, G: GoalKind<'tcx>> {
- pub(super) source: G::CandidateSource,
+pub(super) struct Candidate<'tcx> {
+ pub(super) source: CandidateSource,
pub(super) result: CanonicalResponse<'tcx>,
}
-pub(super) trait GoalKind<'tcx>: TypeFoldable<'tcx> + Copy {
- type CandidateSource: Debug + Copy;
+/// Possible ways the given goal can be proven.
+#[derive(Debug, Clone, Copy)]
+pub(super) enum CandidateSource {
+ /// A user written impl.
+ ///
+ /// ## Examples
+ ///
+ /// ```rust
+ /// fn main() {
+ /// let x: Vec<u32> = Vec::new();
+ /// // This uses the impl from the standard library to prove `Vec<T>: Clone`.
+ /// let y = x.clone();
+ /// }
+ /// ```
+ Impl(DefId),
+ /// A builtin impl generated by the compiler. When adding a new special
+ /// trait, try to use actual impls whenever possible. Builtin impls should
+ /// only be used in cases where the impl cannot be manually be written.
+ ///
+ /// Notable examples are auto traits, `Sized`, and `DiscriminantKind`.
+ /// For a list of all traits with builtin impls, check out the
+ /// [`EvalCtxt::assemble_builtin_impl_candidates`] method. Not
+ BuiltinImpl,
+ /// An assumption from the environment.
+ ///
+ /// More precicely we've used the `n-th` assumption in the `param_env`.
+ ///
+ /// ## Examples
+ ///
+ /// ```rust
+ /// fn is_clone<T: Clone>(x: T) -> (T, T) {
+ /// // This uses the assumption `T: Clone` from the `where`-bounds
+ /// // to prove `T: Clone`.
+ /// (x.clone(), x)
+ /// }
+ /// ```
+ ParamEnv(usize),
+ /// If the self type is an alias type, e.g. an opaque type or a projection,
+ /// we know the bounds on that alias to hold even without knowing its concrete
+ /// underlying type.
+ ///
+ /// More precisely this candidate is using the `n-th` bound in the `item_bounds` of
+ /// the self type.
+ ///
+ /// ## Examples
+ ///
+ /// ```rust
+ /// trait Trait {
+ /// type Assoc: Clone;
+ /// }
+ ///
+ /// fn foo<T: Trait>(x: <T as Trait>::Assoc) {
+ /// // We prove `<T as Trait>::Assoc` by looking at the bounds on `Assoc` in
+ /// // in the trait definition.
+ /// let _y = x.clone();
+ /// }
+ /// ```
+ AliasBound(usize),
+}
+pub(super) trait GoalKind<'tcx>: TypeFoldable<'tcx> + Copy {
fn self_ty(self) -> Ty<'tcx>;
fn with_self_ty(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self;
@@ -40,47 +86,40 @@ pub(super) trait GoalKind<'tcx>: TypeFoldable<'tcx> + Copy {
fn trait_def_id(self, tcx: TyCtxt<'tcx>) -> DefId;
fn consider_impl_candidate(
- acx: &mut AssemblyCtxt<'_, 'tcx, Self>,
+ ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
impl_def_id: DefId,
- );
+ ) -> Result<Certainty, NoSolution>;
+
+ fn consider_builtin_sized_candidate(
+ ecx: &mut EvalCtxt<'_, 'tcx>,
+ goal: Goal<'tcx, Self>,
+ ) -> Result<Certainty, NoSolution>;
+
+ fn consider_assumption(
+ ecx: &mut EvalCtxt<'_, 'tcx>,
+ goal: Goal<'tcx, Self>,
+ assumption: ty::Predicate<'tcx>,
+ ) -> Result<Certainty, NoSolution>;
}
-
-/// An abstraction which correctly deals with the canonical results for candidates.
-///
-/// It also deduplicates the behavior between trait and projection predicates.
-pub(super) struct AssemblyCtxt<'a, 'tcx, G: GoalKind<'tcx>> {
- pub(super) cx: &'a mut EvalCtxt<'tcx>,
- pub(super) infcx: &'a InferCtxt<'tcx>,
- var_values: CanonicalVarValues<'tcx>,
- candidates: Vec<Candidate<'tcx, G>>,
-}
-
-impl<'a, 'tcx, G: GoalKind<'tcx>> AssemblyCtxt<'a, 'tcx, G> {
- pub(super) fn assemble_and_evaluate_candidates(
- cx: &'a mut EvalCtxt<'tcx>,
- goal: CanonicalGoal<'tcx, G>,
- ) -> Vec<Candidate<'tcx, G>> {
- let (ref infcx, goal, var_values) =
- cx.tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &goal);
- let mut acx = AssemblyCtxt { cx, infcx, var_values, candidates: Vec::new() };
-
- acx.assemble_candidates_after_normalizing_self_ty(goal);
-
- acx.assemble_impl_candidates(goal);
-
- acx.candidates
- }
-
- pub(super) fn try_insert_candidate(
+impl<'tcx> EvalCtxt<'_, 'tcx> {
+ pub(super) fn assemble_and_evaluate_candidates<G: GoalKind<'tcx>>(
&mut self,
- source: G::CandidateSource,
- certainty: Certainty,
- ) {
- match self.infcx.make_canonical_response(self.var_values.clone(), certainty) {
- Ok(result) => self.candidates.push(Candidate { source, result }),
- Err(NoSolution) => debug!(?source, ?certainty, "failed leakcheck"),
- }
+ goal: Goal<'tcx, G>,
+ ) -> Vec<Candidate<'tcx>> {
+ let mut candidates = Vec::new();
+
+ self.assemble_candidates_after_normalizing_self_ty(goal, &mut candidates);
+
+ self.assemble_impl_candidates(goal, &mut candidates);
+
+ self.assemble_builtin_impl_candidates(goal, &mut candidates);
+
+ self.assemble_param_env_candidates(goal, &mut candidates);
+
+ self.assemble_alias_bound_candidates(goal, &mut candidates);
+
+ candidates
}
/// If the self type of a goal is a projection, computing the relevant candidates is difficult.
@@ -88,8 +127,12 @@ impl<'a, 'tcx, G: GoalKind<'tcx>> AssemblyCtxt<'a, 'tcx, G> {
/// To deal with this, we first try to normalize the self type and add the candidates for the normalized
/// self type to the list of candidates in case that succeeds. Note that we can't just eagerly return in
/// this case as projections as self types add `
- fn assemble_candidates_after_normalizing_self_ty(&mut self, goal: Goal<'tcx, G>) {
- let tcx = self.cx.tcx;
+ fn assemble_candidates_after_normalizing_self_ty<G: GoalKind<'tcx>>(
+ &mut self,
+ goal: Goal<'tcx, G>,
+ candidates: &mut Vec<Candidate<'tcx>>,
+ ) {
+ let tcx = self.tcx();
// FIXME: We also have to normalize opaque types, not sure where to best fit that in.
let &ty::Alias(ty::Projection, projection_ty) = goal.predicate.self_ty().kind() else {
return
@@ -103,45 +146,136 @@ impl<'a, 'tcx, G: GoalKind<'tcx>> AssemblyCtxt<'a, 'tcx, G> {
term: normalized_ty.into(),
}),
);
- let normalization_certainty =
- match self.cx.evaluate_goal(&self.infcx, normalizes_to_goal) {
- Ok((_, certainty)) => certainty,
- Err(NoSolution) => return,
- };
+ let normalization_certainty = match self.evaluate_goal(normalizes_to_goal) {
+ Ok((_, certainty)) => certainty,
+ Err(NoSolution) => return,
+ };
// NOTE: Alternatively we could call `evaluate_goal` here and only have a `Normalized` candidate.
- // This doesn't work as long as we use `CandidateSource` in both winnowing and to resolve associated items.
+ // This doesn't work as long as we use `CandidateSource` in winnowing.
let goal = goal.with(tcx, goal.predicate.with_self_ty(tcx, normalized_ty));
- let mut orig_values = OriginalQueryValues::default();
- let goal = self.infcx.canonicalize_query(goal, &mut orig_values);
- let normalized_candidates =
- AssemblyCtxt::assemble_and_evaluate_candidates(self.cx, goal);
-
- // Map each candidate from being canonical wrt the current inference context to being
- // canonical wrt the caller.
- for Candidate { source, result } in normalized_candidates {
- self.infcx.probe(|_| {
- let candidate_certainty =
- instantiate_canonical_query_response(&self.infcx, &orig_values, result);
-
- // FIXME: This is a bit scary if the `normalizes_to_goal` overflows.
- //
- // If we have an ambiguous candidate it hides that normalization
- // caused an overflow which may cause issues.
- self.try_insert_candidate(
- source,
- normalization_certainty.unify_and(candidate_certainty),
- )
- })
+ // FIXME: This is broken if we care about the `usize` of `AliasBound` because the self type
+ // could be normalized to yet another projection with different item bounds.
+ let normalized_candidates = self.assemble_and_evaluate_candidates(goal);
+ for mut normalized_candidate in normalized_candidates {
+ normalized_candidate.result =
+ normalized_candidate.result.unchecked_map(|mut response| {
+ // FIXME: This currently hides overflow in the normalization step of the self type
+ // which is probably wrong. Maybe `unify_and` should actually keep overflow as
+ // we treat it as non-fatal anyways.
+ response.certainty = response.certainty.unify_and(normalization_certainty);
+ response
+ });
+ candidates.push(normalized_candidate);
}
})
}
- fn assemble_impl_candidates(&mut self, goal: Goal<'tcx, G>) {
- self.cx.tcx.for_each_relevant_impl(
- goal.predicate.trait_def_id(self.cx.tcx),
+ fn assemble_impl_candidates<G: GoalKind<'tcx>>(
+ &mut self,
+ goal: Goal<'tcx, G>,
+ candidates: &mut Vec<Candidate<'tcx>>,
+ ) {
+ let tcx = self.tcx();
+ tcx.for_each_relevant_impl(
+ goal.predicate.trait_def_id(tcx),
goal.predicate.self_ty(),
- |impl_def_id| G::consider_impl_candidate(self, goal, impl_def_id),
+ |impl_def_id| match G::consider_impl_candidate(self, goal, impl_def_id)
+ .and_then(|certainty| self.make_canonical_response(certainty))
+ {
+ Ok(result) => candidates
+ .push(Candidate { source: CandidateSource::Impl(impl_def_id), result }),
+ Err(NoSolution) => (),
+ },
);
}
+
+ fn assemble_builtin_impl_candidates<G: GoalKind<'tcx>>(
+ &mut self,
+ goal: Goal<'tcx, G>,
+ candidates: &mut Vec<Candidate<'tcx>>,
+ ) {
+ let lang_items = self.tcx().lang_items();
+ let trait_def_id = goal.predicate.trait_def_id(self.tcx());
+ let result = if lang_items.sized_trait() == Some(trait_def_id) {
+ G::consider_builtin_sized_candidate(self, goal)
+ } else {
+ Err(NoSolution)
+ };
+
+ match result.and_then(|certainty| self.make_canonical_response(certainty)) {
+ Ok(result) => {
+ candidates.push(Candidate { source: CandidateSource::BuiltinImpl, result })
+ }
+ Err(NoSolution) => (),
+ }
+ }
+
+ fn assemble_param_env_candidates<G: GoalKind<'tcx>>(
+ &mut self,
+ goal: Goal<'tcx, G>,
+ candidates: &mut Vec<Candidate<'tcx>>,
+ ) {
+ for (i, assumption) in goal.param_env.caller_bounds().iter().enumerate() {
+ match G::consider_assumption(self, goal, assumption)
+ .and_then(|certainty| self.make_canonical_response(certainty))
+ {
+ Ok(result) => {
+ candidates.push(Candidate { source: CandidateSource::ParamEnv(i), result })
+ }
+ Err(NoSolution) => (),
+ }
+ }
+ }
+
+ fn assemble_alias_bound_candidates<G: GoalKind<'tcx>>(
+ &mut self,
+ goal: Goal<'tcx, G>,
+ candidates: &mut Vec<Candidate<'tcx>>,
+ ) {
+ let alias_ty = match goal.predicate.self_ty().kind() {
+ ty::Bool
+ | ty::Char
+ | ty::Int(_)
+ | ty::Uint(_)
+ | ty::Float(_)
+ | ty::Adt(_, _)
+ | ty::Foreign(_)
+ | ty::Str
+ | ty::Array(_, _)
+ | ty::Slice(_)
+ | ty::RawPtr(_)
+ | ty::Ref(_, _, _)
+ | ty::FnDef(_, _)
+ | ty::FnPtr(_)
+ | ty::Dynamic(..)
+ | ty::Closure(..)
+ | ty::Generator(..)
+ | ty::GeneratorWitness(_)
+ | ty::Never
+ | ty::Tuple(_)
+ | ty::Param(_)
+ | ty::Placeholder(..)
+ | ty::Infer(_)
+ | ty::Error(_) => return,
+ ty::Bound(..) => bug!("unexpected bound type: {goal:?}"),
+ ty::Alias(_, alias_ty) => alias_ty,
+ };
+
+ for (i, (assumption, _)) in self
+ .tcx()
+ .bound_explicit_item_bounds(alias_ty.def_id)
+ .subst_iter_copied(self.tcx(), alias_ty.substs)
+ .enumerate()
+ {
+ match G::consider_assumption(self, goal, assumption)
+ .and_then(|certainty| self.make_canonical_response(certainty))
+ {
+ Ok(result) => {
+ candidates.push(Candidate { source: CandidateSource::AliasBound(i), result })
+ }
+ Err(NoSolution) => (),
+ }
+ }
+ }
}
diff --git a/compiler/rustc_trait_selection/src/solve/cache.rs b/compiler/rustc_trait_selection/src/solve/cache.rs
deleted file mode 100644
index f1ee73a5b85..00000000000
--- a/compiler/rustc_trait_selection/src/solve/cache.rs
+++ /dev/null
@@ -1,291 +0,0 @@
-//! This module both handles the global cache which stores "finished" goals,
-//! and the provisional cache which contains partially computed goals.
-//!
-//! The provisional cache is necessary when dealing with coinductive cycles.
-//!
-//! For more information about the provisional cache and coinduction in general,
-//! check out the relevant section of the rustc-dev-guide.
-//!
-//! FIXME(@lcnr): Write that section, feel free to ping me if you need help here
-//! before then or if I still haven't done that before January 2023.
-use super::overflow::OverflowData;
-use super::{CanonicalGoal, Certainty, MaybeCause, Response};
-use super::{EvalCtxt, QueryResult};
-
-use rustc_data_structures::fx::FxHashMap;
-use rustc_infer::infer::canonical::{Canonical, CanonicalVarKind, CanonicalVarValues};
-use rustc_middle::ty::{self, TyCtxt};
-use std::{cmp::Ordering, collections::hash_map::Entry};
-
-#[derive(Debug, Clone)]
-struct ProvisionalEntry<'tcx> {
- // In case we have a coinductive cycle, this is the
- // the currently least restrictive result of this goal.
- response: QueryResult<'tcx>,
- // The lowest element on the stack on which this result
- // relies on. Starts out as just being the depth at which
- // we've proven this obligation, but gets lowered to the
- // depth of another goal if we rely on it in a cycle.
- depth: usize,
-}
-
-struct StackElem<'tcx> {
- goal: CanonicalGoal<'tcx>,
- has_been_used: bool,
-}
-
-/// The cache used for goals which are currently in progress or which depend
-/// on in progress results.
-///
-/// Once we're done with a goal we can store it in the global trait solver
-/// cache of the `TyCtxt`. For goals which we're currently proving, or which
-/// have only been proven via a coinductive cycle using a goal still on our stack
-/// we have to use this separate data structure.
-///
-/// The current data structure is not perfect, so there may still be room for
-/// improvement here. We have the following requirements:
-///
-/// ## Is there is a provisional entry for the given goal:
-///
-/// ```ignore (for syntax highlighting)
-/// self.entries.get(goal)
-/// ```
-///
-/// ## Get all goals on the stack involved in a cycle:
-///
-/// ```ignore (for syntax highlighting)
-/// let entry = self.entries.get(goal).unwrap();
-/// let involved_goals = self.stack.iter().skip(entry.depth);
-/// ```
-///
-/// ## Capping the depth of all entries
-///
-/// Needed whenever we encounter a cycle. The current implementation always
-/// iterates over all entries instead of only the ones with a larger depth.
-/// Changing this may result in notable performance improvements.
-///
-/// ```ignore (for syntax highlighting)
-/// let cycle_depth = self.entries.get(goal).unwrap().depth;
-/// for e in &mut self.entries {
-/// e.depth = e.depth.min(cycle_depth);
-/// }
-/// ```
-///
-/// ## Checking whether we have to rerun the current goal
-///
-/// A goal has to be rerun if its provisional result was used in a cycle
-/// and that result is different from its final result. We update
-/// [StackElem::has_been_used] for the deepest stack element involved in a cycle.
-///
-/// ## Moving all finished goals into the global cache
-///
-/// If `stack_elem.has_been_used` is true, iterate over all entries, moving the ones
-/// with equal depth. If not, simply move this single entry.
-pub(super) struct ProvisionalCache<'tcx> {
- stack: Vec<StackElem<'tcx>>,
- entries: FxHashMap<CanonicalGoal<'tcx>, ProvisionalEntry<'tcx>>,
-}
-
-impl<'tcx> ProvisionalCache<'tcx> {
- pub(super) fn empty() -> ProvisionalCache<'tcx> {
- ProvisionalCache { stack: Vec::new(), entries: Default::default() }
- }
-
- pub(super) fn current_depth(&self) -> usize {
- self.stack.len()
- }
-}
-
-impl<'tcx> EvalCtxt<'tcx> {
- /// Tries putting the new goal on the stack, returning an error if it is already cached.
- ///
- /// This correctly updates the provisional cache if there is a cycle.
- pub(super) fn try_push_stack(
- &mut self,
- goal: CanonicalGoal<'tcx>,
- ) -> Result<(), QueryResult<'tcx>> {
- // FIXME: start by checking the global cache
-
- // Look at the provisional cache to check for cycles.
- let cache = &mut self.provisional_cache;
- match cache.entries.entry(goal) {
- // No entry, simply push this goal on the stack after dealing with overflow.
- Entry::Vacant(v) => {
- if self.overflow_data.has_overflow(cache.stack.len()) {
- return Err(self.deal_with_overflow(goal));
- }
-
- v.insert(ProvisionalEntry {
- response: response_no_constraints(self.tcx, goal, Certainty::Yes),
- depth: cache.stack.len(),
- });
- cache.stack.push(StackElem { goal, has_been_used: false });
- Ok(())
- }
- // We have a nested goal which relies on a goal `root` deeper in the stack.
- //
- // We first store that we may have to rerun `evaluate_goal` for `root` in case the
- // provisional response is not equal to the final response. We also update the depth
- // of all goals which recursively depend on our current goal to depend on `root`
- // instead.
- //
- // Finally we can return either the provisional response for that goal if we have a
- // coinductive cycle or an ambiguous result if the cycle is inductive.
- Entry::Occupied(entry) => {
- // FIXME: `ProvisionalEntry` should be `Copy`.
- let entry = entry.get().clone();
- cache.stack[entry.depth].has_been_used = true;
- for provisional_entry in cache.entries.values_mut() {
- provisional_entry.depth = provisional_entry.depth.min(entry.depth);
- }
-
- // NOTE: The goals on the stack aren't the only goals involved in this cycle.
- // We can also depend on goals which aren't part of the stack but coinductively
- // depend on the stack themselves. We already checked whether all the goals
- // between these goals and their root on the stack. This means that as long as
- // each goal in a cycle is checked for coinductivity by itself simply checking
- // the stack is enough.
- if cache.stack[entry.depth..]
- .iter()
- .all(|g| g.goal.value.predicate.is_coinductive(self.tcx))
- {
- Err(entry.response)
- } else {
- Err(response_no_constraints(
- self.tcx,
- goal,
- Certainty::Maybe(MaybeCause::Ambiguity),
- ))
- }
- }
- }
- }
-
- /// We cannot simply store the result of [EvalCtxt::compute_goal] as we have to deal with
- /// coinductive cycles.
- ///
- /// When we encounter a coinductive cycle, we have to prove the final result of that cycle
- /// while we are still computing that result. Because of this we continously recompute the
- /// cycle until the result of the previous iteration is equal to the final result, at which
- /// point we are done.
- ///
- /// This function returns `true` if we were able to finalize the goal and `false` if it has
- /// updated the provisional cache and we have to recompute the current goal.
- ///
- /// FIXME: Refer to the rustc-dev-guide entry once it exists.
- pub(super) fn try_finalize_goal(
- &mut self,
- actual_goal: CanonicalGoal<'tcx>,
- response: QueryResult<'tcx>,
- ) -> bool {
- let cache = &mut self.provisional_cache;
- let StackElem { goal, has_been_used } = cache.stack.pop().unwrap();
- assert_eq!(goal, actual_goal);
-
- let provisional_entry = cache.entries.get_mut(&goal).unwrap();
- // Check whether the current stack entry is the root of a cycle.
- //
- // If so, we either move all participants of that cycle to the global cache
- // or, in case the provisional response used in the cycle is not equal to the
- // final response, have to recompute the goal after updating the provisional
- // response to the final response of this iteration.
- if has_been_used {
- if provisional_entry.response == response {
- // We simply drop all entries according to an immutable condition, so
- // query instability is not a concern here.
- #[allow(rustc::potential_query_instability)]
- cache.entries.retain(|goal, entry| match entry.depth.cmp(&cache.stack.len()) {
- Ordering::Less => true,
- Ordering::Equal => {
- Self::try_move_finished_goal_to_global_cache(
- self.tcx,
- &mut self.overflow_data,
- &cache.stack,
- // FIXME: these should be `Copy` :(
- goal.clone(),
- entry.response.clone(),
- );
- false
- }
- Ordering::Greater => bug!("entry with greater depth than the current leaf"),
- });
-
- true
- } else {
- provisional_entry.response = response;
- cache.stack.push(StackElem { goal, has_been_used: false });
- false
- }
- } else {
- Self::try_move_finished_goal_to_global_cache(
- self.tcx,
- &mut self.overflow_data,
- &cache.stack,
- goal,
- response,
- );
- cache.entries.remove(&goal);
- true
- }
- }
-
- fn try_move_finished_goal_to_global_cache(
- tcx: TyCtxt<'tcx>,
- overflow_data: &mut OverflowData,
- stack: &[StackElem<'tcx>],
- goal: CanonicalGoal<'tcx>,
- response: QueryResult<'tcx>,
- ) {
- // We move goals to the global cache if we either did not hit an overflow or if it's
- // the root goal as that will now always hit the same overflow limit.
- //
- // NOTE: We cannot move any non-root goals to the global cache even if their final result
- // isn't impacted by the overflow as that goal still has unstable query dependencies
- // because it didn't go its full depth.
- //
- // FIXME(@lcnr): We could still cache subtrees which are not impacted by overflow though.
- // Tracking that info correctly isn't trivial, so I haven't implemented it for now.
- let should_cache_globally = !overflow_data.did_overflow() || stack.is_empty();
- if should_cache_globally {
- // FIXME: move the provisional entry to the global cache.
- let _ = (tcx, goal, response);
- }
- }
-}
-
-pub(super) fn response_no_constraints<'tcx>(
- tcx: TyCtxt<'tcx>,
- goal: Canonical<'tcx, impl Sized>,
- certainty: Certainty,
-) -> QueryResult<'tcx> {
- let var_values = goal
- .variables
- .iter()
- .enumerate()
- .map(|(i, info)| match info.kind {
- CanonicalVarKind::Ty(_) | CanonicalVarKind::PlaceholderTy(_) => {
- tcx.mk_ty(ty::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i).into())).into()
- }
- CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => {
- let br = ty::BoundRegion {
- var: ty::BoundVar::from_usize(i),
- kind: ty::BrAnon(i as u32, None),
- };
- tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br)).into()
- }
- CanonicalVarKind::Const(_, ty) | CanonicalVarKind::PlaceholderConst(_, ty) => tcx
- .mk_const(ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i)), ty)
- .into(),
- })
- .collect();
-
- Ok(Canonical {
- max_universe: goal.max_universe,
- variables: goal.variables,
- value: Response {
- var_values: CanonicalVarValues { var_values },
- external_constraints: Default::default(),
- certainty,
- },
- })
-}
diff --git a/compiler/rustc_trait_selection/src/solve/fulfill.rs b/compiler/rustc_trait_selection/src/solve/fulfill.rs
index dfc2b5ed329..b086c0684d2 100644
--- a/compiler/rustc_trait_selection/src/solve/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/solve/fulfill.rs
@@ -10,7 +10,7 @@ use rustc_infer::{
};
use rustc_middle::ty;
-use super::{Certainty, EvalCtxt};
+use super::{search_graph, Certainty, EvalCtxt};
/// A trait engine using the new trait solver.
///
@@ -67,9 +67,10 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentCtxt<'tcx> {
let mut has_changed = false;
for obligation in mem::take(&mut self.obligations) {
- let mut cx = EvalCtxt::new(infcx.tcx);
- let (changed, certainty) = match cx.evaluate_goal(infcx, obligation.clone().into())
- {
+ let goal = obligation.clone().into();
+ let search_graph = &mut search_graph::SearchGraph::new(infcx.tcx);
+ let mut ecx = EvalCtxt::new_outside_solver(infcx, search_graph);
+ let (changed, certainty) = match ecx.evaluate_goal(goal) {
Ok(result) => result,
Err(NoSolution) => {
errors.push(FulfillmentError {
diff --git a/compiler/rustc_trait_selection/src/solve/infcx_ext.rs b/compiler/rustc_trait_selection/src/solve/infcx_ext.rs
index 436f4eea662..9b7feb50537 100644
--- a/compiler/rustc_trait_selection/src/solve/infcx_ext.rs
+++ b/compiler/rustc_trait_selection/src/solve/infcx_ext.rs
@@ -1,23 +1,30 @@
-use rustc_infer::infer::canonical::CanonicalVarValues;
+use rustc_infer::infer::at::ToTrace;
use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
-use rustc_infer::infer::InferCtxt;
+use rustc_infer::infer::{InferCtxt, InferOk};
use rustc_infer::traits::query::NoSolution;
-use rustc_middle::ty::Ty;
+use rustc_infer::traits::ObligationCause;
+use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
+use rustc_middle::ty::{self, Ty};
use rustc_span::DUMMY_SP;
-use crate::solve::ExternalConstraints;
-
-use super::{Certainty, QueryResult, Response};
+use super::Goal;
/// Methods used inside of the canonical queries of the solver.
+///
+/// Most notably these do not care about diagnostics information.
+/// If you find this while looking for methods to use outside of the
+/// solver, you may look at the implementation of these method for
+/// help.
pub(super) trait InferCtxtExt<'tcx> {
fn next_ty_infer(&self) -> Ty<'tcx>;
+ fn next_const_infer(&self, ty: Ty<'tcx>) -> ty::Const<'tcx>;
- fn make_canonical_response(
+ fn eq<T: ToTrace<'tcx>>(
&self,
- var_values: CanonicalVarValues<'tcx>,
- certainty: Certainty,
- ) -> QueryResult<'tcx>;
+ param_env: ty::ParamEnv<'tcx>,
+ lhs: T,
+ rhs: T,
+ ) -> Result<Vec<Goal<'tcx, ty::Predicate<'tcx>>>, NoSolution>;
}
impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
@@ -27,29 +34,29 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
span: DUMMY_SP,
})
}
+ fn next_const_infer(&self, ty: Ty<'tcx>) -> ty::Const<'tcx> {
+ self.next_const_var(
+ ty,
+ ConstVariableOrigin { kind: ConstVariableOriginKind::MiscVariable, span: DUMMY_SP },
+ )
+ }
- fn make_canonical_response(
+ #[instrument(level = "debug", skip(self, param_env), ret)]
+ fn eq<T: ToTrace<'tcx>>(
&self,
- var_values: CanonicalVarValues<'tcx>,
- certainty: Certainty,
- ) -> QueryResult<'tcx> {
- let external_constraints = take_external_constraints(self)?;
-
- Ok(self.canonicalize_response(Response { var_values, external_constraints, certainty }))
+ param_env: ty::ParamEnv<'tcx>,
+ lhs: T,
+ rhs: T,
+ ) -> Result<Vec<Goal<'tcx, ty::Predicate<'tcx>>>, NoSolution> {
+ self.at(&ObligationCause::dummy(), param_env)
+ .define_opaque_types(false)
+ .eq(lhs, rhs)
+ .map(|InferOk { value: (), obligations }| {
+ obligations.into_iter().map(|o| o.into()).collect()
+ })
+ .map_err(|e| {
+ debug!(?e, "failed to equate");
+ NoSolution
+ })
}
}
-
-#[instrument(level = "debug", skip(infcx), ret)]
-fn take_external_constraints<'tcx>(
- infcx: &InferCtxt<'tcx>,
-) -> Result<ExternalConstraints<'tcx>, NoSolution> {
- let region_obligations = infcx.take_registered_region_obligations();
- let opaque_types = infcx.take_opaque_types_for_query_response();
- Ok(ExternalConstraints {
- // FIXME: Now that's definitely wrong :)
- //
- // Should also do the leak check here I think
- regions: drop(region_obligations),
- opaque_types,
- })
-}
diff --git a/compiler/rustc_trait_selection/src/solve/mod.rs b/compiler/rustc_trait_selection/src/solve/mod.rs
index 80775b7aaf2..579cd6a2d59 100644
--- a/compiler/rustc_trait_selection/src/solve/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/mod.rs
@@ -19,27 +19,23 @@
use std::mem;
+use rustc_infer::infer::canonical::{Canonical, CanonicalVarKind, CanonicalVarValues};
use rustc_infer::infer::canonical::{OriginalQueryValues, QueryRegionConstraints, QueryResponse};
use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::Obligation;
use rustc_middle::infer::canonical::Certainty as OldCertainty;
-use rustc_middle::infer::canonical::{Canonical, CanonicalVarValues};
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_middle::ty::{RegionOutlivesPredicate, ToPredicate, TypeOutlivesPredicate};
use rustc_span::DUMMY_SP;
use crate::traits::ObligationCause;
-use self::cache::response_no_constraints;
-use self::infcx_ext::InferCtxtExt;
-
mod assembly;
-mod cache;
mod fulfill;
mod infcx_ext;
-mod overflow;
mod project_goals;
+mod search_graph;
mod trait_goals;
pub use fulfill::FulfillmentCtxt;
@@ -146,45 +142,42 @@ pub trait TyCtxtExt<'tcx> {
impl<'tcx> TyCtxtExt<'tcx> for TyCtxt<'tcx> {
fn evaluate_goal(self, goal: CanonicalGoal<'tcx>) -> QueryResult<'tcx> {
- let mut cx = EvalCtxt::new(self);
- cx.evaluate_canonical_goal(goal)
+ let mut search_graph = search_graph::SearchGraph::new(self);
+ EvalCtxt::evaluate_canonical_goal(self, &mut search_graph, goal)
}
}
-struct EvalCtxt<'tcx> {
- tcx: TyCtxt<'tcx>,
+struct EvalCtxt<'a, 'tcx> {
+ infcx: &'a InferCtxt<'tcx>,
+ var_values: CanonicalVarValues<'tcx>,
- provisional_cache: cache::ProvisionalCache<'tcx>,
- overflow_data: overflow::OverflowData,
+ search_graph: &'a mut search_graph::SearchGraph<'tcx>,
}
-impl<'tcx> EvalCtxt<'tcx> {
- fn new(tcx: TyCtxt<'tcx>) -> EvalCtxt<'tcx> {
- EvalCtxt {
- tcx,
- provisional_cache: cache::ProvisionalCache::empty(),
- overflow_data: overflow::OverflowData::new(tcx),
- }
+impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
+ fn tcx(&self) -> TyCtxt<'tcx> {
+ self.infcx.tcx
}
- /// Recursively evaluates `goal`, returning whether any inference vars have
- /// been constrained and the certainty of the result.
- fn evaluate_goal(
- &mut self,
- infcx: &InferCtxt<'tcx>,
- goal: Goal<'tcx, ty::Predicate<'tcx>>,
- ) -> Result<(bool, Certainty), NoSolution> {
- let mut orig_values = OriginalQueryValues::default();
- let canonical_goal = infcx.canonicalize_query(goal, &mut orig_values);
- let canonical_response = self.evaluate_canonical_goal(canonical_goal)?;
- Ok((
- !canonical_response.value.var_values.is_identity(),
- instantiate_canonical_query_response(infcx, &orig_values, canonical_response),
- ))
+ /// Creates a new evaluation context outside of the trait solver.
+ ///
+ /// With this solver making a canonical response doesn't make much sense.
+ /// The `search_graph` for this solver has to be completely empty.
+ fn new_outside_solver(
+ infcx: &'a InferCtxt<'tcx>,
+ search_graph: &'a mut search_graph::SearchGraph<'tcx>,
+ ) -> EvalCtxt<'a, 'tcx> {
+ assert!(search_graph.is_empty());
+ EvalCtxt { infcx, var_values: CanonicalVarValues::dummy(), search_graph }
}
- fn evaluate_canonical_goal(&mut self, goal: CanonicalGoal<'tcx>) -> QueryResult<'tcx> {
- match self.try_push_stack(goal) {
+ #[instrument(level = "debug", skip(tcx, search_graph), ret)]
+ fn evaluate_canonical_goal(
+ tcx: TyCtxt<'tcx>,
+ search_graph: &'a mut search_graph::SearchGraph<'tcx>,
+ canonical_goal: CanonicalGoal<'tcx>,
+ ) -> QueryResult<'tcx> {
+ match search_graph.try_push_stack(tcx, canonical_goal) {
Ok(()) => {}
// Our goal is already on the stack, eager return.
Err(response) => return response,
@@ -195,41 +188,61 @@ impl<'tcx> EvalCtxt<'tcx> {
//
// FIXME: Similar to `evaluate_all`, this has to check for overflow.
loop {
- let result = self.compute_goal(goal);
+ let (ref infcx, goal, var_values) =
+ tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical_goal);
+ let mut ecx = EvalCtxt { infcx, var_values, search_graph };
+ let result = ecx.compute_goal(goal);
// FIXME: `Response` should be `Copy`
- if self.try_finalize_goal(goal, result.clone()) {
+ if search_graph.try_finalize_goal(tcx, canonical_goal, result.clone()) {
return result;
}
}
}
- fn compute_goal(&mut self, canonical_goal: CanonicalGoal<'tcx>) -> QueryResult<'tcx> {
- // WARNING: We're looking at a canonical value without instantiating it here.
- //
- // We have to be incredibly careful to not change the order of bound variables or
- // remove any. As we go from `Goal<'tcx, Predicate>` to `Goal` with the variants
- // of `PredicateKind` this is the case and it is and faster than instantiating and
- // recanonicalizing.
- let Goal { param_env, predicate } = canonical_goal.value;
+ fn make_canonical_response(&self, certainty: Certainty) -> QueryResult<'tcx> {
+ let external_constraints = take_external_constraints(self.infcx)?;
- if let Some(kind) = predicate.kind().no_bound_vars_ignoring_escaping(self.tcx) {
+ Ok(self.infcx.canonicalize_response(Response {
+ var_values: self.var_values.clone(),
+ external_constraints,
+ certainty,
+ }))
+ }
+
+ /// Recursively evaluates `goal`, returning whether any inference vars have
+ /// been constrained and the certainty of the result.
+ fn evaluate_goal(
+ &mut self,
+ goal: Goal<'tcx, ty::Predicate<'tcx>>,
+ ) -> Result<(bool, Certainty), NoSolution> {
+ let mut orig_values = OriginalQueryValues::default();
+ let canonical_goal = self.infcx.canonicalize_query(goal, &mut orig_values);
+ let canonical_response =
+ EvalCtxt::evaluate_canonical_goal(self.tcx(), self.search_graph, canonical_goal)?;
+ Ok((
+ !canonical_response.value.var_values.is_identity(),
+ instantiate_canonical_query_response(self.infcx, &orig_values, canonical_response),
+ ))
+ }
+
+ fn compute_goal(&mut self, goal: Goal<'tcx, ty::Predicate<'tcx>>) -> QueryResult<'tcx> {
+ let Goal { param_env, predicate } = goal;
+ let kind = predicate.kind();
+ if let Some(kind) = kind.no_bound_vars() {
match kind {
- ty::PredicateKind::Clause(ty::Clause::Trait(predicate)) => self.compute_trait_goal(
- canonical_goal.unchecked_rebind(Goal { param_env, predicate }),
- ),
- ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) => self
- .compute_projection_goal(
- canonical_goal.unchecked_rebind(Goal { param_env, predicate }),
- ),
- ty::PredicateKind::Clause(ty::Clause::TypeOutlives(predicate)) => self
- .compute_type_outlives_goal(
- canonical_goal.unchecked_rebind(Goal { param_env, predicate }),
- ),
- ty::PredicateKind::Clause(ty::Clause::RegionOutlives(predicate)) => self
- .compute_region_outlives_goal(
- canonical_goal.unchecked_rebind(Goal { param_env, predicate }),
- ),
+ ty::PredicateKind::Clause(ty::Clause::Trait(predicate)) => {
+ self.compute_trait_goal(Goal { param_env, predicate })
+ }
+ ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) => {
+ self.compute_projection_goal(Goal { param_env, predicate })
+ }
+ ty::PredicateKind::Clause(ty::Clause::TypeOutlives(predicate)) => {
+ self.compute_type_outlives_goal(Goal { param_env, predicate })
+ }
+ ty::PredicateKind::Clause(ty::Clause::RegionOutlives(predicate)) => {
+ self.compute_region_outlives_goal(Goal { param_env, predicate })
+ }
// FIXME: implement these predicates :)
ty::PredicateKind::WellFormed(_)
| ty::PredicateKind::ObjectSafe(_)
@@ -239,49 +252,41 @@ impl<'tcx> EvalCtxt<'tcx> {
| ty::PredicateKind::ConstEvaluatable(_)
| ty::PredicateKind::ConstEquate(_, _)
| ty::PredicateKind::TypeWellFormedFromEnv(_)
- | ty::PredicateKind::Ambiguous => {
- // FIXME
- response_no_constraints(self.tcx, canonical_goal, Certainty::Yes)
- }
+ | ty::PredicateKind::Ambiguous => self.make_canonical_response(Certainty::Yes),
}
} else {
- let (infcx, goal, var_values) =
- self.tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical_goal);
- let kind = infcx.replace_bound_vars_with_placeholders(goal.predicate.kind());
- let goal = goal.with(self.tcx, ty::Binder::dummy(kind));
- let (_, certainty) = self.evaluate_goal(&infcx, goal)?;
- infcx.make_canonical_response(var_values, certainty)
+ let kind = self.infcx.replace_bound_vars_with_placeholders(kind);
+ let goal = goal.with(self.tcx(), ty::Binder::dummy(kind));
+ let (_, certainty) = self.evaluate_goal(goal)?;
+ self.make_canonical_response(certainty)
}
}
fn compute_type_outlives_goal(
&mut self,
- goal: CanonicalGoal<'tcx, TypeOutlivesPredicate<'tcx>>,
+ _goal: Goal<'tcx, TypeOutlivesPredicate<'tcx>>,
) -> QueryResult<'tcx> {
- // FIXME
- response_no_constraints(self.tcx, goal, Certainty::Yes)
+ self.make_canonical_response(Certainty::Yes)
}
fn compute_region_outlives_goal(
&mut self,
- goal: CanonicalGoal<'tcx, RegionOutlivesPredicate<'tcx>>,
+ _goal: Goal<'tcx, RegionOutlivesPredicate<'tcx>>,
) -> QueryResult<'tcx> {
- // FIXME
- response_no_constraints(self.tcx, goal, Certainty::Yes)
+ self.make_canonical_response(Certainty::Yes)
}
}
-impl<'tcx> EvalCtxt<'tcx> {
+impl<'tcx> EvalCtxt<'_, 'tcx> {
fn evaluate_all(
&mut self,
- infcx: &InferCtxt<'tcx>,
mut goals: Vec<Goal<'tcx, ty::Predicate<'tcx>>>,
) -> Result<Certainty, NoSolution> {
let mut new_goals = Vec::new();
self.repeat_while_none(|this| {
let mut has_changed = Err(Certainty::Yes);
for goal in goals.drain(..) {
- let (changed, certainty) = match this.evaluate_goal(infcx, goal) {
+ let (changed, certainty) = match this.evaluate_goal(goal) {
Ok(result) => result,
Err(NoSolution) => return Some(Err(NoSolution)),
};
@@ -310,6 +315,21 @@ impl<'tcx> EvalCtxt<'tcx> {
}
}
+#[instrument(level = "debug", skip(infcx), ret)]
+fn take_external_constraints<'tcx>(
+ infcx: &InferCtxt<'tcx>,
+) -> Result<ExternalConstraints<'tcx>, NoSolution> {
+ let region_obligations = infcx.take_registered_region_obligations();
+ let opaque_types = infcx.take_opaque_types_for_query_response();
+ Ok(ExternalConstraints {
+ // FIXME: Now that's definitely wrong :)
+ //
+ // Should also do the leak check here I think
+ regions: drop(region_obligations),
+ opaque_types,
+ })
+}
+
fn instantiate_canonical_query_response<'tcx>(
infcx: &InferCtxt<'tcx>,
original_values: &OriginalQueryValues<'tcx>,
@@ -334,3 +354,40 @@ fn instantiate_canonical_query_response<'tcx>(
assert!(obligations.is_empty());
value
}
+
+pub(super) fn response_no_constraints<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ goal: Canonical<'tcx, impl Sized>,
+ certainty: Certainty,
+) -> QueryResult<'tcx> {
+ let var_values = goal
+ .variables
+ .iter()
+ .enumerate()
+ .map(|(i, info)| match info.kind {
+ CanonicalVarKind::Ty(_) | CanonicalVarKind::PlaceholderTy(_) => {
+ tcx.mk_ty(ty::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i).into())).into()
+ }
+ CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => {
+ let br = ty::BoundRegion {
+ var: ty::BoundVar::from_usize(i),
+ kind: ty::BrAnon(i as u32, None),
+ };
+ tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br)).into()
+ }
+ CanonicalVarKind::Const(_, ty) | CanonicalVarKind::PlaceholderConst(_, ty) => tcx
+ .mk_const(ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i)), ty)
+ .into(),
+ })
+ .collect();
+
+ Ok(Canonical {
+ max_universe: goal.max_universe,
+ variables: goal.variables,
+ value: Response {
+ var_values: CanonicalVarValues { var_values },
+ external_constraints: Default::default(),
+ certainty,
+ },
+ })
+}
diff --git a/compiler/rustc_trait_selection/src/solve/project_goals.rs b/compiler/rustc_trait_selection/src/solve/project_goals.rs
index d2f2e78f555..0658836fb9c 100644
--- a/compiler/rustc_trait_selection/src/solve/project_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/project_goals.rs
@@ -1,38 +1,123 @@
use crate::traits::{specialization_graph, translate_substs};
-use super::assembly::{self, AssemblyCtxt};
-use super::{CanonicalGoal, EvalCtxt, Goal, QueryResult};
+use super::assembly::{self, Candidate, CandidateSource};
+use super::infcx_ext::InferCtxtExt;
+use super::{Certainty, EvalCtxt, Goal, MaybeCause, QueryResult};
use rustc_errors::ErrorGuaranteed;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::DefId;
-use rustc_infer::infer::{InferCtxt, InferOk};
+use rustc_infer::infer::InferCtxt;
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::specialization_graph::LeafDef;
-use rustc_infer::traits::{ObligationCause, Reveal};
+use rustc_infer::traits::Reveal;
use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
-use rustc_middle::ty::ProjectionPredicate;
use rustc_middle::ty::TypeVisitable;
use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty::{ProjectionPredicate, TypeSuperVisitable, TypeVisitor};
use rustc_span::DUMMY_SP;
use std::iter;
+use std::ops::ControlFlow;
-#[allow(dead_code)] // FIXME: implement and use all variants.
-#[derive(Debug, Clone, Copy)]
-pub(super) enum CandidateSource {
- Impl(DefId),
- ParamEnv(usize),
- Builtin,
-}
-
-type Candidate<'tcx> = assembly::Candidate<'tcx, ProjectionPredicate<'tcx>>;
-
-impl<'tcx> EvalCtxt<'tcx> {
+impl<'tcx> EvalCtxt<'_, 'tcx> {
pub(super) fn compute_projection_goal(
&mut self,
- goal: CanonicalGoal<'tcx, ProjectionPredicate<'tcx>>,
+ goal: Goal<'tcx, ProjectionPredicate<'tcx>>,
) -> QueryResult<'tcx> {
- let candidates = AssemblyCtxt::assemble_and_evaluate_candidates(self, goal);
- self.merge_project_candidates(candidates)
+ // To only compute normalization ones for each projection we only
+ // normalize if the expected term is an unconstrained inference variable.
+ //
+ // E.g. for `<T as Trait>::Assoc = u32` we recursively compute the goal
+ // `exists<U> <T as Trait>::Assoc = U` and then take the resulting type for
+ // `U` and equate it with `u32`. This means that we don't need a separate
+ // projection cache in the solver.
+ if self.term_is_fully_unconstrained(goal) {
+ let candidates = self.assemble_and_evaluate_candidates(goal);
+ self.merge_project_candidates(candidates)
+ } else {
+ let predicate = goal.predicate;
+ let unconstrained_rhs = match predicate.term.unpack() {
+ ty::TermKind::Ty(_) => self.infcx.next_ty_infer().into(),
+ ty::TermKind::Const(ct) => self.infcx.next_const_infer(ct.ty()).into(),
+ };
+ let unconstrained_predicate = ty::Clause::Projection(ProjectionPredicate {
+ projection_ty: goal.predicate.projection_ty,
+ term: unconstrained_rhs,
+ });
+ let (_has_changed, normalize_certainty) =
+ self.evaluate_goal(goal.with(self.tcx(), unconstrained_predicate))?;
+
+ let nested_eq_goals =
+ self.infcx.eq(goal.param_env, unconstrained_rhs, predicate.term)?;
+ let eval_certainty = self.evaluate_all(nested_eq_goals)?;
+ self.make_canonical_response(normalize_certainty.unify_and(eval_certainty))
+ }
+ }
+
+ /// Is the projection predicate is of the form `exists<T> <Ty as Trait>::Assoc = T`.
+ ///
+ /// This is the case if the `term` is an inference variable in the innermost universe
+ /// and does not occur in any other part of the predicate.
+ fn term_is_fully_unconstrained(&self, goal: Goal<'tcx, ProjectionPredicate<'tcx>>) -> bool {
+ let infcx = self.infcx;
+ let term_is_infer = match goal.predicate.term.unpack() {
+ ty::TermKind::Ty(ty) => {
+ if let &ty::Infer(ty::TyVar(vid)) = ty.kind() {
+ match infcx.probe_ty_var(vid) {
+ Ok(value) => bug!("resolved var in query: {goal:?} {value:?}"),
+ Err(universe) => universe == infcx.universe(),
+ }
+ } else {
+ false
+ }
+ }
+ ty::TermKind::Const(ct) => {
+ if let ty::ConstKind::Infer(ty::InferConst::Var(vid)) = ct.kind() {
+ match self.infcx.probe_const_var(vid) {
+ Ok(value) => bug!("resolved var in query: {goal:?} {value:?}"),
+ Err(universe) => universe == infcx.universe(),
+ }
+ } else {
+ false
+ }
+ }
+ };
+
+ // Guard against `<T as Trait<?0>>::Assoc = ?0>`.
+ struct ContainsTerm<'tcx> {
+ term: ty::Term<'tcx>,
+ }
+ impl<'tcx> TypeVisitor<'tcx> for ContainsTerm<'tcx> {
+ type BreakTy = ();
+ fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
+ if t.needs_infer() {
+ if ty::Term::from(t) == self.term {
+ ControlFlow::BREAK
+ } else {
+ t.super_visit_with(self)
+ }
+ } else {
+ ControlFlow::CONTINUE
+ }
+ }
+
+ fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
+ if c.needs_infer() {
+ if ty::Term::from(c) == self.term {
+ ControlFlow::BREAK
+ } else {
+ c.super_visit_with(self)
+ }
+ } else {
+ ControlFlow::CONTINUE
+ }
+ }
+ }
+
+ let mut visitor = ContainsTerm { term: goal.predicate.term };
+
+ term_is_infer
+ && goal.predicate.projection_ty.visit_with(&mut visitor).is_continue()
+ && goal.param_env.visit_with(&mut visitor).is_continue()
}
fn merge_project_candidates(
@@ -83,14 +168,13 @@ impl<'tcx> EvalCtxt<'tcx> {
match (candidate.source, other.source) {
(CandidateSource::Impl(_), _)
| (CandidateSource::ParamEnv(_), _)
- | (CandidateSource::Builtin, _) => unimplemented!(),
+ | (CandidateSource::BuiltinImpl, _)
+ | (CandidateSource::AliasBound(_), _) => unimplemented!(),
}
}
}
impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
- type CandidateSource = CandidateSource;
-
fn self_ty(self) -> Ty<'tcx> {
self.self_ty()
}
@@ -104,33 +188,26 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
}
fn consider_impl_candidate(
- acx: &mut AssemblyCtxt<'_, 'tcx, ProjectionPredicate<'tcx>>,
+ ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, ProjectionPredicate<'tcx>>,
impl_def_id: DefId,
- ) {
- let tcx = acx.cx.tcx;
+ ) -> Result<Certainty, NoSolution> {
+ let tcx = ecx.tcx();
+
let goal_trait_ref = goal.predicate.projection_ty.trait_ref(tcx);
let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsPlaceholder };
if iter::zip(goal_trait_ref.substs, impl_trait_ref.skip_binder().substs)
.any(|(goal, imp)| !drcx.generic_args_may_unify(goal, imp))
{
- return;
+ return Err(NoSolution);
}
- acx.infcx.probe(|_| {
- let impl_substs = acx.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
+ ecx.infcx.probe(|_| {
+ let impl_substs = ecx.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
let impl_trait_ref = impl_trait_ref.subst(tcx, impl_substs);
- let Ok(InferOk { obligations, .. }) = acx
- .infcx
- .at(&ObligationCause::dummy(), goal.param_env)
- .define_opaque_types(false)
- .eq(goal_trait_ref, impl_trait_ref)
- .map_err(|e| debug!("failed to equate trait refs: {e:?}"))
- else {
- return
- };
+ let mut nested_goals = ecx.infcx.eq(goal.param_env, goal_trait_ref, impl_trait_ref)?;
let where_clause_bounds = tcx
.predicates_of(impl_def_id)
.instantiate(tcx, impl_substs)
@@ -138,17 +215,21 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
.into_iter()
.map(|pred| goal.with(tcx, pred));
- let nested_goals = obligations.into_iter().map(|o| o.into()).chain(where_clause_bounds).collect();
- let Ok(trait_ref_certainty) = acx.cx.evaluate_all(acx.infcx, nested_goals) else { return };
+ nested_goals.extend(where_clause_bounds);
+ let trait_ref_certainty = ecx.evaluate_all(nested_goals)?;
+ // In case the associated item is hidden due to specialization, we have to
+ // return ambiguity this would otherwise be incomplete, resulting in
+ // unsoundness during coherence (#105782).
let Some(assoc_def) = fetch_eligible_assoc_item_def(
- acx.infcx,
+ ecx.infcx,
goal.param_env,
goal_trait_ref,
goal.predicate.def_id(),
impl_def_id
- ) else {
- return
+ )? else {
+ let certainty = Certainty::Maybe(MaybeCause::Ambiguity);
+ return Ok(trait_ref_certainty.unify_and(certainty));
};
if !assoc_def.item.defaultness(tcx).has_value() {
@@ -174,7 +255,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
impl_substs,
);
let substs = translate_substs(
- acx.infcx,
+ ecx.infcx,
goal.param_env,
impl_def_id,
impl_substs_with_gat,
@@ -185,7 +266,8 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
let is_const = matches!(tcx.def_kind(assoc_def.item.def_id), DefKind::AssocConst);
let ty = tcx.bound_type_of(assoc_def.item.def_id);
let term: ty::EarlyBinder<ty::Term<'tcx>> = if is_const {
- let identity_substs = ty::InternalSubsts::identity_for_item(tcx, assoc_def.item.def_id);
+ let identity_substs =
+ ty::InternalSubsts::identity_for_item(tcx, assoc_def.item.def_id);
let did = ty::WithOptConstParam::unknown(assoc_def.item.def_id);
let kind =
ty::ConstKind::Unevaluated(ty::UnevaluatedConst::new(did, identity_substs));
@@ -194,23 +276,38 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
ty.map_bound(|ty| ty.into())
};
- let Ok(InferOk { obligations, .. }) = acx
+ // The term of our goal should be fully unconstrained, so this should never fail.
+ //
+ // It can however be ambiguous when the resolved type is a projection.
+ let nested_goals = ecx
.infcx
- .at(&ObligationCause::dummy(), goal.param_env)
- .define_opaque_types(false)
- .eq(goal.predicate.term, term.subst(tcx, substs))
- .map_err(|e| debug!("failed to equate trait refs: {e:?}"))
- else {
- return
- };
+ .eq(goal.param_env, goal.predicate.term, term.subst(tcx, substs))
+ .expect("failed to unify with unconstrained term");
+ let rhs_certainty =
+ ecx.evaluate_all(nested_goals).expect("failed to unify with unconstrained term");
- let nested_goals = obligations.into_iter().map(|o| o.into()).collect();
- let Ok(rhs_certainty) = acx.cx.evaluate_all(acx.infcx, nested_goals) else { return };
-
- let certainty = trait_ref_certainty.unify_and(rhs_certainty);
- acx.try_insert_candidate(CandidateSource::Impl(impl_def_id), certainty);
+ Ok(trait_ref_certainty.unify_and(rhs_certainty))
})
}
+
+ fn consider_builtin_sized_candidate(
+ _ecx: &mut EvalCtxt<'_, 'tcx>,
+ goal: Goal<'tcx, Self>,
+ ) -> Result<Certainty, NoSolution> {
+ bug!("`Sized` does not have an associated type: {:?}", goal);
+ }
+
+ fn consider_assumption(
+ _ecx: &mut EvalCtxt<'_, 'tcx>,
+ _goal: Goal<'tcx, Self>,
+ assumption: ty::Predicate<'tcx>,
+ ) -> Result<Certainty, NoSolution> {
+ if let Some(_poly_projection_pred) = assumption.to_opt_poly_projection_pred() {
+ unimplemented!()
+ } else {
+ Err(NoSolution)
+ }
+ }
}
/// This behavior is also implemented in `rustc_ty_utils` and in the old `project` code.
@@ -224,10 +321,9 @@ fn fetch_eligible_assoc_item_def<'tcx>(
goal_trait_ref: ty::TraitRef<'tcx>,
trait_assoc_def_id: DefId,
impl_def_id: DefId,
-) -> Option<LeafDef> {
+) -> Result<Option<LeafDef>, NoSolution> {
let node_item = specialization_graph::assoc_def(infcx.tcx, impl_def_id, trait_assoc_def_id)
- .map_err(|ErrorGuaranteed { .. }| ())
- .ok()?;
+ .map_err(|ErrorGuaranteed { .. }| NoSolution)?;
let eligible = if node_item.is_final() {
// Non-specializable items are always projectable.
@@ -246,5 +342,5 @@ fn fetch_eligible_assoc_item_def<'tcx>(
}
};
- if eligible { Some(node_item) } else { None }
+ if eligible { Ok(Some(node_item)) } else { Ok(None) }
}
diff --git a/compiler/rustc_trait_selection/src/solve/search_graph/cache.rs b/compiler/rustc_trait_selection/src/solve/search_graph/cache.rs
new file mode 100644
index 00000000000..730a8e61258
--- /dev/null
+++ b/compiler/rustc_trait_selection/src/solve/search_graph/cache.rs
@@ -0,0 +1,123 @@
+//! This module both handles the global cache which stores "finished" goals,
+//! and the provisional cache which contains partially computed goals.
+//!
+//! The provisional cache is necessary when dealing with coinductive cycles.
+//!
+//! For more information about the provisional cache and coinduction in general,
+//! check out the relevant section of the rustc-dev-guide.
+//!
+//! FIXME(@lcnr): Write that section, feel free to ping me if you need help here
+//! before then or if I still haven't done that before January 2023.
+use super::overflow::OverflowData;
+use super::StackDepth;
+use crate::solve::{CanonicalGoal, QueryResult};
+use rustc_data_structures::fx::FxHashMap;
+use rustc_index::vec::IndexVec;
+use rustc_middle::ty::TyCtxt;
+
+rustc_index::newtype_index! {
+ pub struct EntryIndex {}
+}
+
+#[derive(Debug, Clone)]
+pub(super) struct ProvisionalEntry<'tcx> {
+ // In case we have a coinductive cycle, this is the
+ // the currently least restrictive result of this goal.
+ pub(super) response: QueryResult<'tcx>,
+ // In case of a cycle, the position of deepest stack entry involved
+ // in that cycle. This is monotonically decreasing in the stack as all
+ // elements between the current stack element in the deepest stack entry
+ // involved have to also be involved in that cycle.
+ //
+ // We can only move entries to the global cache once we're complete done
+ // with the cycle. If this entry has not been involved in a cycle,
+ // this is just its own depth.
+ pub(super) depth: StackDepth,
+
+ // The goal for this entry. Should always be equal to the corresponding goal
+ // in the lookup table.
+ pub(super) goal: CanonicalGoal<'tcx>,
+}
+
+pub(super) struct ProvisionalCache<'tcx> {
+ pub(super) entries: IndexVec<EntryIndex, ProvisionalEntry<'tcx>>,
+ // FIXME: This is only used to quickly check whether a given goal
+ // is in the cache. We should experiment with using something like
+ // `SsoHashSet` here because in most cases there are only a few entries.
+ pub(super) lookup_table: FxHashMap<CanonicalGoal<'tcx>, EntryIndex>,
+}
+
+impl<'tcx> ProvisionalCache<'tcx> {
+ pub(super) fn empty() -> ProvisionalCache<'tcx> {
+ ProvisionalCache { entries: Default::default(), lookup_table: Default::default() }
+ }
+
+ pub(super) fn is_empty(&self) -> bool {
+ self.entries.is_empty() && self.lookup_table.is_empty()
+ }
+
+ /// Adds a dependency from the current leaf to `target` in the cache
+ /// to prevent us from moving any goals which depend on the current leaf
+ /// to the global cache while we're still computing `target`.
+ ///
+ /// Its important to note that `target` may already be part of a different cycle.
+ /// In this case we have to ensure that we also depend on all other goals
+ /// in the existing cycle in addition to the potentially direct cycle with `target`.
+ pub(super) fn add_dependency_of_leaf_on(&mut self, target: EntryIndex) {
+ let depth = self.entries[target].depth;
+ for provisional_entry in &mut self.entries.raw[target.index()..] {
+ // The depth of `target` is the position of the deepest goal in the stack
+ // on which `target` depends. That goal is the `root` of this cycle.
+ //
+ // Any entry which was added after `target` is either on the stack itself
+ // at which point its depth is definitely at least as high as the depth of
+ // `root`. If it's not on the stack itself it has to depend on a goal
+ // between `root` and `leaf`. If it were to depend on a goal deeper in the
+ // stack than `root`, then `root` would also depend on that goal, at which
+ // point `root` wouldn't be the root anymore.
+ debug_assert!(provisional_entry.depth >= depth);
+ provisional_entry.depth = depth;
+ }
+
+ // We only update entries which were added after `target` as no other
+ // entry should have a higher depth.
+ //
+ // Any entry which previously had a higher depth than target has to
+ // be between `target` and `root`. Because of this we would have updated
+ // its depth when calling `add_dependency_of_leaf_on(root)` for `target`.
+ if cfg!(debug_assertions) {
+ self.entries.iter().all(|e| e.depth <= depth);
+ }
+ }
+
+ pub(super) fn depth(&self, entry_index: EntryIndex) -> StackDepth {
+ self.entries[entry_index].depth
+ }
+
+ pub(super) fn provisional_result(&self, entry_index: EntryIndex) -> QueryResult<'tcx> {
+ self.entries[entry_index].response.clone()
+ }
+}
+
+pub(super) fn try_move_finished_goal_to_global_cache<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ overflow_data: &mut OverflowData,
+ stack: &IndexVec<super::StackDepth, super::StackElem<'tcx>>,
+ goal: CanonicalGoal<'tcx>,
+ response: QueryResult<'tcx>,
+) {
+ // We move goals to the global cache if we either did not hit an overflow or if it's
+ // the root goal as that will now always hit the same overflow limit.
+ //
+ // NOTE: We cannot move any non-root goals to the global cache even if their final result
+ // isn't impacted by the overflow as that goal still has unstable query dependencies
+ // because it didn't go its full depth.
+ //
+ // FIXME(@lcnr): We could still cache subtrees which are not impacted by overflow though.
+ // Tracking that info correctly isn't trivial, so I haven't implemented it for now.
+ let should_cache_globally = !overflow_data.did_overflow() || stack.is_empty();
+ if should_cache_globally {
+ // FIXME: move the provisional entry to the global cache.
+ let _ = (tcx, goal, response);
+ }
+}
diff --git a/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs b/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs
new file mode 100644
index 00000000000..0030e9aa3e5
--- /dev/null
+++ b/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs
@@ -0,0 +1,178 @@
+mod cache;
+mod overflow;
+
+use self::cache::ProvisionalEntry;
+use super::{CanonicalGoal, Certainty, MaybeCause, QueryResult};
+use cache::ProvisionalCache;
+use overflow::OverflowData;
+use rustc_index::vec::IndexVec;
+use rustc_middle::ty::TyCtxt;
+use std::collections::hash_map::Entry;
+
+rustc_index::newtype_index! {
+ pub struct StackDepth {}
+}
+
+struct StackElem<'tcx> {
+ goal: CanonicalGoal<'tcx>,
+ has_been_used: bool,
+}
+
+pub(super) struct SearchGraph<'tcx> {
+ /// The stack of goals currently being computed.
+ ///
+ /// An element is *deeper* in the stack if its index is *lower*.
+ stack: IndexVec<StackDepth, StackElem<'tcx>>,
+ overflow_data: OverflowData,
+ provisional_cache: ProvisionalCache<'tcx>,
+}
+
+impl<'tcx> SearchGraph<'tcx> {
+ pub(super) fn new(tcx: TyCtxt<'tcx>) -> SearchGraph<'tcx> {
+ Self {
+ stack: Default::default(),
+ overflow_data: OverflowData::new(tcx),
+ provisional_cache: ProvisionalCache::empty(),
+ }
+ }
+
+ pub(super) fn is_empty(&self) -> bool {
+ self.stack.is_empty()
+ && self.provisional_cache.is_empty()
+ && !self.overflow_data.did_overflow()
+ }
+
+ /// Tries putting the new goal on the stack, returning an error if it is already cached.
+ ///
+ /// This correctly updates the provisional cache if there is a cycle.
+ pub(super) fn try_push_stack(
+ &mut self,
+ tcx: TyCtxt<'tcx>,
+ goal: CanonicalGoal<'tcx>,
+ ) -> Result<(), QueryResult<'tcx>> {
+ // FIXME: start by checking the global cache
+
+ // Look at the provisional cache to check for cycles.
+ let cache = &mut self.provisional_cache;
+ match cache.lookup_table.entry(goal) {
+ // No entry, simply push this goal on the stack after dealing with overflow.
+ Entry::Vacant(v) => {
+ if self.overflow_data.has_overflow(self.stack.len()) {
+ return Err(self.deal_with_overflow(tcx, goal));
+ }
+
+ let depth = self.stack.push(StackElem { goal, has_been_used: false });
+ let response = super::response_no_constraints(tcx, goal, Certainty::Yes);
+ let entry_index = cache.entries.push(ProvisionalEntry { response, depth, goal });
+ v.insert(entry_index);
+ Ok(())
+ }
+ // We have a nested goal which relies on a goal `root` deeper in the stack.
+ //
+ // We first store that we may have to rerun `evaluate_goal` for `root` in case the
+ // provisional response is not equal to the final response. We also update the depth
+ // of all goals which recursively depend on our current goal to depend on `root`
+ // instead.
+ //
+ // Finally we can return either the provisional response for that goal if we have a
+ // coinductive cycle or an ambiguous result if the cycle is inductive.
+ Entry::Occupied(entry_index) => {
+ let entry_index = *entry_index.get();
+
+ cache.add_dependency_of_leaf_on(entry_index);
+ let stack_depth = cache.depth(entry_index);
+
+ self.stack[stack_depth].has_been_used = true;
+ // NOTE: The goals on the stack aren't the only goals involved in this cycle.
+ // We can also depend on goals which aren't part of the stack but coinductively
+ // depend on the stack themselves. We already checked whether all the goals
+ // between these goals and their root on the stack. This means that as long as
+ // each goal in a cycle is checked for coinductivity by itself, simply checking
+ // the stack is enough.
+ if self.stack.raw[stack_depth.index()..]
+ .iter()
+ .all(|g| g.goal.value.predicate.is_coinductive(tcx))
+ {
+ Err(cache.provisional_result(entry_index))
+ } else {
+ Err(super::response_no_constraints(
+ tcx,
+ goal,
+ Certainty::Maybe(MaybeCause::Overflow),
+ ))
+ }
+ }
+ }
+ }
+
+ /// We cannot simply store the result of [super::EvalCtxt::compute_goal] as we have to deal with
+ /// coinductive cycles.
+ ///
+ /// When we encounter a coinductive cycle, we have to prove the final result of that cycle
+ /// while we are still computing that result. Because of this we continously recompute the
+ /// cycle until the result of the previous iteration is equal to the final result, at which
+ /// point we are done.
+ ///
+ /// This function returns `true` if we were able to finalize the goal and `false` if it has
+ /// updated the provisional cache and we have to recompute the current goal.
+ ///
+ /// FIXME: Refer to the rustc-dev-guide entry once it exists.
+ pub(super) fn try_finalize_goal(
+ &mut self,
+ tcx: TyCtxt<'tcx>,
+ actual_goal: CanonicalGoal<'tcx>,
+ response: QueryResult<'tcx>,
+ ) -> bool {
+ let StackElem { goal, has_been_used } = self.stack.pop().unwrap();
+ assert_eq!(goal, actual_goal);
+
+ let cache = &mut self.provisional_cache;
+ let provisional_entry_index = *cache.lookup_table.get(&goal).unwrap();
+ let provisional_entry = &mut cache.entries[provisional_entry_index];
+ let depth = provisional_entry.depth;
+ // Was the current goal the root of a cycle and was the provisional response
+ // different from the final one.
+ if has_been_used && provisional_entry.response != response {
+ // If so, update the provisional reponse for this goal...
+ provisional_entry.response = response;
+ // ...remove all entries whose result depends on this goal
+ // from the provisional cache...
+ //
+ // That's not completely correct, as a nested goal can also
+ // depend on a goal which is lower in the stack so it doesn't
+ // actually depend on the current goal. This should be fairly
+ // rare and is hopefully not relevant for performance.
+ #[allow(rustc::potential_query_instability)]
+ cache.lookup_table.retain(|_key, index| *index <= provisional_entry_index);
+ cache.entries.truncate(provisional_entry_index.index() + 1);
+
+ // ...and finally push our goal back on the stack and reevaluate it.
+ self.stack.push(StackElem { goal, has_been_used: false });
+ false
+ } else {
+ // If not, we're done with this goal.
+ //
+ // Check whether that this goal doesn't depend on a goal deeper on the stack
+ // and if so, move it and all nested goals to the global cache.
+ //
+ // Note that if any nested goal were to depend on something deeper on the stack,
+ // this would have also updated the depth of the current goal.
+ if depth == self.stack.next_index() {
+ for (i, entry) in cache.entries.drain_enumerated(provisional_entry_index.index()..)
+ {
+ let actual_index = cache.lookup_table.remove(&entry.goal);
+ debug_assert_eq!(Some(i), actual_index);
+ debug_assert!(entry.depth == depth);
+ cache::try_move_finished_goal_to_global_cache(
+ tcx,
+ &mut self.overflow_data,
+ &self.stack,
+ entry.goal,
+ entry.response,
+ );
+ }
+ }
+ true
+ }
+ }
+}
diff --git a/compiler/rustc_trait_selection/src/solve/overflow.rs b/compiler/rustc_trait_selection/src/solve/search_graph/overflow.rs
similarity index 74%
rename from compiler/rustc_trait_selection/src/solve/overflow.rs
rename to compiler/rustc_trait_selection/src/solve/search_graph/overflow.rs
index 8bbb9f63e78..1dd3894c91a 100644
--- a/compiler/rustc_trait_selection/src/solve/overflow.rs
+++ b/compiler/rustc_trait_selection/src/solve/search_graph/overflow.rs
@@ -3,8 +3,8 @@ use rustc_infer::traits::query::NoSolution;
use rustc_middle::ty::TyCtxt;
use rustc_session::Limit;
-use super::cache::response_no_constraints;
-use super::{Certainty, EvalCtxt, MaybeCause, QueryResult};
+use super::SearchGraph;
+use crate::solve::{response_no_constraints, Certainty, EvalCtxt, MaybeCause, QueryResult};
/// When detecting a solver overflow, we return ambiguity. Overflow can be
/// *hidden* by either a fatal error in an **AND** or a trivial success in an **OR**.
@@ -50,32 +50,35 @@ impl OverflowData {
}
}
-impl<'tcx> EvalCtxt<'tcx> {
- pub(super) fn deal_with_overflow(
+impl<'tcx> SearchGraph<'tcx> {
+ pub fn deal_with_overflow(
&mut self,
+ tcx: TyCtxt<'tcx>,
goal: Canonical<'tcx, impl Sized>,
) -> QueryResult<'tcx> {
self.overflow_data.deal_with_overflow();
- response_no_constraints(self.tcx, goal, Certainty::Maybe(MaybeCause::Overflow))
+ response_no_constraints(tcx, goal, Certainty::Maybe(MaybeCause::Overflow))
}
+}
+impl<'tcx> EvalCtxt<'_, 'tcx> {
/// A `while`-loop which tracks overflow.
- pub(super) fn repeat_while_none(
+ pub fn repeat_while_none(
&mut self,
mut loop_body: impl FnMut(&mut Self) -> Option<Result<Certainty, NoSolution>>,
) -> Result<Certainty, NoSolution> {
- let start_depth = self.overflow_data.additional_depth;
- let depth = self.provisional_cache.current_depth();
- while !self.overflow_data.has_overflow(depth) {
+ let start_depth = self.search_graph.overflow_data.additional_depth;
+ let depth = self.search_graph.stack.len();
+ while !self.search_graph.overflow_data.has_overflow(depth) {
if let Some(result) = loop_body(self) {
- self.overflow_data.additional_depth = start_depth;
+ self.search_graph.overflow_data.additional_depth = start_depth;
return result;
}
- self.overflow_data.additional_depth += 1;
+ self.search_graph.overflow_data.additional_depth += 1;
}
- self.overflow_data.additional_depth = start_depth;
- self.overflow_data.deal_with_overflow();
+ self.search_graph.overflow_data.additional_depth = start_depth;
+ self.search_graph.overflow_data.deal_with_overflow();
Ok(Certainty::Maybe(MaybeCause::Overflow))
}
}
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
index a43fef5cdb0..bbe175d5cc8 100644
--- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
@@ -2,58 +2,17 @@
use std::iter;
-use super::assembly::{self, AssemblyCtxt};
-use super::{CanonicalGoal, EvalCtxt, Goal, QueryResult};
+use super::assembly::{self, Candidate, CandidateSource};
+use super::infcx_ext::InferCtxtExt;
+use super::{Certainty, EvalCtxt, Goal, QueryResult};
use rustc_hir::def_id::DefId;
-use rustc_infer::infer::InferOk;
use rustc_infer::traits::query::NoSolution;
-use rustc_infer::traits::ObligationCause;
use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
use rustc_middle::ty::TraitPredicate;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_span::DUMMY_SP;
-#[allow(dead_code)] // FIXME: implement and use all variants.
-#[derive(Debug, Clone, Copy)]
-pub(super) enum CandidateSource {
- /// Some user-defined impl with the given `DefId`.
- Impl(DefId),
- /// The n-th caller bound in the `param_env` of our goal.
- ///
- /// This is pretty much always a bound from the `where`-clauses of the
- /// currently checked item.
- ParamEnv(usize),
- /// A bound on the `self_ty` in case it is a projection or an opaque type.
- ///
- /// # Examples
- ///
- /// ```ignore (for syntax highlighting)
- /// trait Trait {
- /// type Assoc: OtherTrait;
- /// }
- /// ```
- ///
- /// We know that `<Whatever as Trait>::Assoc: OtherTrait` holds by looking at
- /// the bounds on `Trait::Assoc`.
- AliasBound(usize),
- /// A builtin implementation for some specific traits, used in cases
- /// where we cannot rely an ordinary library implementations.
- ///
- /// The most notable examples are `Sized`, `Copy` and `Clone`. This is also
- /// used for the `DiscriminantKind` and `Pointee` trait, both of which have
- /// an associated type.
- Builtin,
- /// An automatic impl for an auto trait, e.g. `Send`. These impls recursively look
- /// at the constituent types of the `self_ty` to check whether the auto trait
- /// is implemented for those.
- AutoImpl,
-}
-
-type Candidate<'tcx> = assembly::Candidate<'tcx, TraitPredicate<'tcx>>;
-
impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
- type CandidateSource = CandidateSource;
-
fn self_ty(self) -> Ty<'tcx> {
self.self_ty()
}
@@ -67,55 +26,63 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
}
fn consider_impl_candidate(
- acx: &mut AssemblyCtxt<'_, 'tcx, Self>,
+ ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, TraitPredicate<'tcx>>,
impl_def_id: DefId,
- ) {
- let tcx = acx.cx.tcx;
+ ) -> Result<Certainty, NoSolution> {
+ let tcx = ecx.tcx();
let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsPlaceholder };
if iter::zip(goal.predicate.trait_ref.substs, impl_trait_ref.skip_binder().substs)
.any(|(goal, imp)| !drcx.generic_args_may_unify(goal, imp))
{
- return;
+ return Err(NoSolution);
}
- acx.infcx.probe(|_| {
- let impl_substs = acx.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
+ ecx.infcx.probe(|_| {
+ let impl_substs = ecx.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
let impl_trait_ref = impl_trait_ref.subst(tcx, impl_substs);
- let Ok(InferOk { obligations, .. }) = acx
- .infcx
- .at(&ObligationCause::dummy(), goal.param_env)
- .define_opaque_types(false)
- .eq(goal.predicate.trait_ref, impl_trait_ref)
- .map_err(|e| debug!("failed to equate trait refs: {e:?}"))
- else {
- return
- };
+ let mut nested_goals =
+ ecx.infcx.eq(goal.param_env, goal.predicate.trait_ref, impl_trait_ref)?;
let where_clause_bounds = tcx
.predicates_of(impl_def_id)
.instantiate(tcx, impl_substs)
.predicates
.into_iter()
.map(|pred| goal.with(tcx, pred));
-
- let nested_goals =
- obligations.into_iter().map(|o| o.into()).chain(where_clause_bounds).collect();
-
- let Ok(certainty) = acx.cx.evaluate_all(acx.infcx, nested_goals) else { return };
- acx.try_insert_candidate(CandidateSource::Impl(impl_def_id), certainty);
+ nested_goals.extend(where_clause_bounds);
+ ecx.evaluate_all(nested_goals)
})
}
+
+ fn consider_builtin_sized_candidate(
+ _ecx: &mut EvalCtxt<'_, 'tcx>,
+ _goal: Goal<'tcx, Self>,
+ ) -> Result<Certainty, NoSolution> {
+ unimplemented!();
+ }
+
+ fn consider_assumption(
+ _ecx: &mut EvalCtxt<'_, 'tcx>,
+ _goal: Goal<'tcx, Self>,
+ assumption: ty::Predicate<'tcx>,
+ ) -> Result<Certainty, NoSolution> {
+ if let Some(_poly_trait_pred) = assumption.to_opt_poly_trait_pred() {
+ unimplemented!()
+ } else {
+ Err(NoSolution)
+ }
+ }
}
-impl<'tcx> EvalCtxt<'tcx> {
+impl<'tcx> EvalCtxt<'_, 'tcx> {
pub(super) fn compute_trait_goal(
&mut self,
- goal: CanonicalGoal<'tcx, TraitPredicate<'tcx>>,
+ goal: Goal<'tcx, TraitPredicate<'tcx>>,
) -> QueryResult<'tcx> {
- let candidates = AssemblyCtxt::assemble_and_evaluate_candidates(self, goal);
+ let candidates = self.assemble_and_evaluate_candidates(goal);
self.merge_trait_candidates_discard_reservation_impls(candidates)
}
@@ -169,14 +136,13 @@ impl<'tcx> EvalCtxt<'tcx> {
(CandidateSource::Impl(_), _)
| (CandidateSource::ParamEnv(_), _)
| (CandidateSource::AliasBound(_), _)
- | (CandidateSource::Builtin, _)
- | (CandidateSource::AutoImpl, _) => unimplemented!(),
+ | (CandidateSource::BuiltinImpl, _) => unimplemented!(),
}
}
fn discard_reservation_impl(&self, candidate: Candidate<'tcx>) -> Candidate<'tcx> {
if let CandidateSource::Impl(def_id) = candidate.source {
- if let ty::ImplPolarity::Reservation = self.tcx.impl_polarity(def_id) {
+ if let ty::ImplPolarity::Reservation = self.tcx().impl_polarity(def_id) {
debug!("Selected reservation impl");
// FIXME: reduce candidate to ambiguous
// FIXME: replace `var_values` with identity, yeet external constraints.